In general, noise intermixed to a TV signal or a signal recorded or reproduced on or from a magnetic tape for a video tape recorder causes noise contamination in an operating state of a television set or a recorded state of the magnetic tape. Particularly, in a case of such a TV signal, serious contamination is likely to occur at a weak electric field of the signal.
Such serious noise is typically an impulse noise such as a white impulse noise and a black impulse noise. Also, a minute noise level contained in a high-frequency component of the TV signal causes a problem in receiving the TV signal.
According to a typical method for eliminating such an impulse noise, a fixed window is set in the signal containing the noise component and, then, the noise is simply averaged or substituted by an average value or by proper pixels by means of a median filter.
With such a conventional method, however, a vertical high frequency component of the image signal is undesirably damaged and, hence, the image is confused unexpectedly.